I witnessed the same type thing around 1990 at the ramp at Buster Boyd. It was crazy cold so hardly anyone at the ramp. I noticed a boat going in circles but it took me a min to realize it was a bad situation. The guy had on a life vest and was maybe 100ft off the shore when I saw him. In that situation the throttle was closing slowly due to the bouncing of the boat and eventually went to an idle. The guy said he had let go of the wheel and the motor suddenly turned and threw him out.